Flame scanner fault detection system

ABSTRACT

A system for detecting a fault in the output signal of a flame scanner circuit, the system comprising ball means, normally gravity biased to a nonblocking position, periodically pneumatically activated to intercept, and block, the scanning view of a glow discharge tube detector used to indicate the presence of a flame. A logic circuit having an AND gate receives independent signals from the pneumatic activating means for the ball means (indicating ball means actuation) and from the flame scanner circuit (indicating positive firing of the glow discharge tube detector). The tube detector, of course, should not be firing, and thus signaling the existence of a flame, when its scanning view is blocked by the ball means. If both of the abovementioned signals reach the AND gate at the same instant, the gate will operate to pass a signal to a fault indicator which may operate any suitable alarm means to indicate a fault in the glow discharge tube detector.

3 5 O m 2 6 6 in SR [72] Inventors Vytautas Pileika 3,286,761 l1/l966 Engh 340/214 X West H f 3,300,769 1/1967 Batur 340/270 H r y J h fi h f, 3,339,195 8/1967 Murley, Jr. 340/259 Collll- 3,431,934 3/1969 Riordan 137/624. M X 1967 Primary Examir zer filohn W. Caldwell [45] Patented July 20, 1971 Assistant ExammerPerry Palan [73] Assigns: Combustion Engineering Attorneys-Edward L. Kochey, .lr., Richard H. Bemeilce, Windsor, ComL Lawrence P. [(essler, Carlton F. Bryant, Arthur C. Firl,

Eldon H. Luther, Robert L. Olson and John F. Carney [54] :i DETECTION SYSTEM ABSTRACT: A system for detecting a fault in the output mg lgS.

signal of a flame scanner circuit, the system compnsmg ball U.S. means normally gravity to a nonblocking position, 340/223, 350/266 periodically pneumatically activated to intercept, and block, [5 l I III. Cl G08!) 29/00, the a in i w ofa low di charge tube detector used to in. 00gb l 2 dicate the presence of a flame. A logic circuit having an AND of l4, ate re eive inde endent signals from the pneumatic activat- 258 41; 250/333 UV; ing means for the ball means (indicating ball means actuation) 431/79; 317/130; 328/6; 137/624; 350/266; and from the flame scanner circuit (indicating positive firing 356/207 of the glow discharge tube detector). The tube detector, of course, should not be firing, and thus signaling the existence of [56] References Cited a flame, when its scanning view is blocked by the ball means. If UNITED STATES PATENTS both of the above-mentioned signals reach the AND gate at 3,170,021 2/1965 Bergson 350/266 X the same instant, the gate will operate to pass a signal to a fault 2,763,853 9/1956 Grant, .lr. 340/228 X indicator which may operate any suitable alarm means to in- 3,l43,l6l 8/1964 Graves et al. 340/410 X dicate a fault in the glow discharge tube detector.

FLAME SCANNER FAULT DETECTION SYSTEM BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to flame scanners and more particularly to a means for detecting a fault in the operation thereof.

Flame scanners are used to monitor the presence of a flame in the combustion chamber of a furnace. One common scanner for this purpose uses a glow discharge tube, of the ultraviolet-type for example, mounted in the furnace relative to the burner ofthe furnace and in such a manner so as to be able to see the flame produced by the burner. A flame from the burner will activate the tube in a well-known manner, producing a signal which may be delivered to a flame scanner circuit, such as that by Gilbert in U.S. Pat. No. 3,286,093 assigned to the same assigiee as is this invention. Such a positive indication of flame is necessary so that a cessation thereof may be immediately detected. The operator of a furnace must know when a flame ceases to exist in order to prevent an excessive amount of unburned fuel from accumulating in the combustion chamber. There could be disastrous results if such raw fuel were allowed to accumulate; for example, the fuel could easily be explosively ignited by hot refractory or when an attempt is made to reignite it.

Although glow discharge tube detector devices provide a relatively simple means of detecting the presence of a flame, they have inherent characteristics which give rise to a need for their being constantly monitored in order to detect faults therein. For example, upon overheating of the tube, a signal may be generated similar in nature to the signal produced when a flame is detected. Therefore, there must be some simple and efficient means by which the tube may be tested while in service to indicate that the tube is functioning properly and not merely giving a positive signal due to a malfunction.

Prior art devices have used periodically activated mechanical means to block the monitoring view of the glow discharge tube detector so that the view from the flame to the tube will be periodically cut off, simulating a flame-out condition. If the tube still generates a signal indicating the presence of a flame while the mechanical blocking means is in this blocking position, an indication of fault in the tube will be recorded. Rotary operated shutter devices have been utilized in the past. The necessary construction thereof, however, is unsuitable for operation in the extreme conditions, such as high temperatures, under which this device must function.

We have therefore developed an extremely simple means for interrupting either periodically or randomly the'view of a glow discharge flame detecting tube so that fault therein may be easily and accurately determined. There is provided a channel intersecting the flame detecting view of the glow discharge tube detector. A pneumatically actuatedv hollow steel ball rides in this channel. The ball, normally gravity biased to a nonblocking position, is of a sufficient diameter so as to enable it to completely block the flame detecting view of the tube detector upon pneumatic actuation to simulate a flame-out condition. A timed solenoid valve is actuated to periodically or randomly admit pressure to this channel to move the ball to interrupt and block the flame detecting view of the tube detector. The solenoid valve will produce a signal indicating actuation thereof. Under normal operating conditions, the flame scanning circuit will produce a signal indicating sensing of flame by the tube detector. Provisions are made to bring these independent signals into a logic circuit containing an AND gate. Thus it can be seen that while the ball is being pneumatically actuated, the flame scanning circuit should produce no signal. If, however, both signals are received by the AND gate simultaneously, there is a fault in the glow discharge tube detector, and the AND gate will allow passage of a signal therethrough, which signal may be used to activate a fault indicator or other suitable alarm means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side view, partly in section and partly schematic, of the flame detecting device and the fault indicating circuitry incorporated in this invention;

FIG. 2 is an enlarged section of the glow discharge tube detector and the pneumatically actuated ball means;

FIG. 3 is a transverse section of the device taken on the line 3-3 of FIG. 2;

FIG. 4 is a transverse section of the device taken on the line 4-4 of FIG. 2; and

FIG. 5 is an end view of a burner nozzle with the flame detecting device installed therein.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters are used to designate like elements, the flame scanning device indicated generally at is shown in FIG. 1 mounted in a burner nozzle tip 12. The device comprises a tubular supporting member indicated generally at I4 having a rigid support member 16 secured in the nozzle tip 12 to one side thereof. Secured to the rigid metal portion 16 by clamps 18 is a flexible metal sleeve 20 which in turn is connected by clamps 22 to a rigid metal pipe 24. Pipe 24 is secured by any suitable means, such as weld 26, to the shell 28 of the air duct supplying air to the burner. Secured on the outer end of pipe 24 is a casting 30 having a chamber 32 communicating with the interior of the tubular member 14 and having an air inlet 34 for directing air from a suitable source of supply to the interior of the tubular member 14. i

An aspirator 36 is provided so as to prevent flame or hot gases from feeding back from the furnace through the tubular member 14 under certain conditions. High pressure is supplied to aspirator 36 through inlet '38 from source 60. Rigid metal pipe 24 has a port 40 located in the side thereof to which high pressure inlet 42 is connected from the same source as that which supplies aspirator 36. The purpose of inlet 42 and its function will be explained hereinbelow.

Cylinder 44, in which is contained the flame monitoring glow discharge tube detector and the pneumatic interrupting means therefor, has connected thereto a flexible conduit 46 encasing electrical conductors 48 and terminating in a rigid section 50 which is threaded into a casting 52. Also connected to cylinder 44 is the flexible conduit 54, which terminates in rigid pipe section 56, which in turn is connected to high pressure inlet 42 through port 40. An air inlet connection 58 is provided in the casting 52 leading into the interior of rigid member 50, flexible member 46 and cylinder 44 to supply a stream of air through the cylinder for cooling purposes.

, The high pressure source 60 which is used to supply pressure to aspirator 36 has a connection provided thereto to supply the pneumatic interrupting device through inlet 42, pipe 56 and flexible connector 54. A timer 62 of either the periodic or random actuation-type is provided to actuate a solenoid valve 64 in the high pressure line of the pneumatic interrupting device as described hereinbelow. Lead 66 is provided for taking a signal indicating positive actuation of the solenoid valve to terminal 68 of a logic circuit containing an AND gate 70. Lead 72 is provided from leads 48 to carry a signal indicating flame detection to the flame scanning circuit 74. Further lead 76 is provided to carry a signal indicating positive flame to AND gate at terminal 78. A fault indicator 80 is connected to the logic circuit AND gate 70 through lead 82. Fault indicator 80 may be connected to any appropriate alarm device 84. Alarm device 84 may be a visual or audible alarm.

The flame monitoring means and pneumatically actuated interrupting means of this invention are best shown in FIG. 2. Within cylinder 44, are located an upper glow discharge tube detector cylinder 86 and a lower ball carrying cylinder 88. Extending from ball carrying cylinder 88 is channel means 90. Channel means 90 is positioned at an angle with respect to the ball carrying cylinder and intersects the axis of the upper tube detector cylinder 86. Within the upper cylinder 86 is located a glow discharge tube detector 92. The tube detector 92 has support pins 94 connected to the tube electrodes 95 at one end and embedded in base 96 at the other end. Base 96 has a central cylindrical bore 98 through which cooling air may be passed for the reasons noted in the above-mentioned Gilbert U.S. Pat. No. 3,241,595. Connected to the tube electrodes 95 through support pins 94 in the base 96 are leads 48 which carry a signal generated by the tube detector 92 in a wellknown manner when a flame is detected. A quartz glass window 100, centered in the tube 86, serves as a means for protecting tube detector 92 from any foreign particles from the furnace which may enter cylinder 44.

A ball 102 rides in lower ball cylinder 88. The ball 102 is shown as a hollow steel sphere, but any other suitable material may be used. The ball 102 is free to move in cylinder 88 and channel 90 against the bias of gravity under influence of the pneumatic pressure. Upon actuation of the solenoid valve 64 by timer 62 as noted above, high pressure from source 60 will be admitted through inlet 42, pipe 56 and conduit 54 to exert a pneumatic force on ball 102 to move the ball 102 in cylinder 88 and channel 90 to portion 104 thereof. Upon release of pressure, the ball 102 will be returned by gravity to lower ball cylinder 88.

FIGS. 3 and 4 show sections through cylinder 44 showing the relative positions of upper cylinder 86 and lower cylinder 88 and the interconnecting channel 90. From these figures it is apparent that actuation of ball 102 by pneumatic pressure will cause the ball to move up into portion 104 of channel 90 to interrupt and block the monitoring view of the glow discharge tube detector 92.

FIG. 5 shows the location of our detector with relation to a particular burner nozzle tip 12. Within the nozzle tip 12 is located a burner nozzle 106. Detector is located as by weld 108 to the nozzle tip 12 in the position shown. When so located, the detector 10 will view the flame area at all times with an unobstructed view. This enables continuous flame monitoring.

With the device thus described, the operation is as follows. Glow discharge tube detector 92 is activated in the wellknown manner so as to yield a positive signal through leads 48 upon detection of a flame as seen through quartz window 100. This signal is transmitted through leads 48 and 72 to flame scanner circuit 74 to monitor the existence of a burner flame. Positive actuation of the tube detector 92 also activates a signal through leads 76 to terminal 78 of the logic circuit AND gate 70. Periodically or randomly as desired, timer 62 actuates solenoid valve 64 to admit high pressure to the lower ball cylinder 88 to move ball 102 in channel 90 to a position at the end 104 thereof. When the timer 62 actuates the solenoid valve 64, a signal will be generated which is carried through lead 66 to terminal 68 of the logic circuit AND gate 70. When at this position, ball 102 will effectively interrupt and block the view of glow discharge tube detector 92. A correct response by the tube detector 92 will then be to give an indication of a flame failure to the flame scanner circuit 74 (i.e., no positive signal). Positive signals from the tube detector 92 and the pneumatic actuating system are, therefore, incongruous and should not exist at the same instant. When. these signals are received simultaneously at the terminals 68 and 78 of the logic circuit AND gate 70, indicating positive actuation of both the timer 62 and the detecting tube 92, the AND gate 70 will pass a signal through lead 82 to the fault indicator 80. Fault indicator 80 will then readout the signal received in any suitable manner, such as by triggering an alarm 84 of either the visual or audible-type as desired. In this manner an immediate indication of fault in the tube detector 92 will be indicated and the furnace operator may act accordingly to prevent damage to the furnace system.

We have found that the flame monitoring device and pneumatically operated fault indicating means associated therewith may be used successfully with a burner of the tilting, tangential type found in large utility boiler furnace systems. The tiltmg angential burners have a tilt angle of i30 from the horizontal. Therefore, in order for ball 102 to properly return to its initial position in lower ball cylinder 88 under the influence of gravity, as explained above, from its interrupting and blocking position at portion 104 of channel 90, the angle of inclination of channel 90 must be greater than 30. We have found that an angle of inclination of 45 will yield a properly functioning device.

From the above description it can be seen that we have invented a simple and economically constructed means of determining a fault in a flame monitoring device which utilizes a glow discharge tube detector. The detecting device may be checked periodically or at random as determined by the operator of the furnace, and may activate any visual or audible alarm means as circumstances dictate. The only moving part of the device is a ball, preferably of the hollow stainless steel construction, yielding a device which is simple to manufacture, and not adversely affected by the extreme conditions found in the nozzle tip where the flame scanner must be located. Furthermore, when in its nonoperative condition, the device does not interfere with the normal operation of the tube detector 92 and the cooling means therefor.

While we have illustrated and described a preferred embodiment of our invention, it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. We therefore do not wish to be limited to the precise details set forth but desire'to avail ourselves of such changes as fall within the purview of our invention.

We claim:

1. in a fault detection apparatus for a flame scanner system being energized by a glow discharge tube detector, the improvement comprising: ball means, ball actuating means, said ball means being located in relationship to said glow discharge tube detector so as to intercept and block the flame detecting view of said tube detector upon periodic positive actuation thereof by said actuating means, a logic circuit having an AND gate therein, said AND gate receiving independent signals from said glow discharge tube detector and said actuating means indicating positive operating conditions thereof, a fault indicating means operatively connected to said logic circuit so as to be activated when said independent signals reach said AND gate simultaneously.

2. Apparatus as claimed in claim 1 wherein said ball actuating means comprises a pneumatic pressure means.

3. Apparatus as claimed in claim 2 wherein said pneumatic pressure means comprises a source of pneumatic pressure, a channel for said ball means, said channel intersecting the path of said flame detecting view of said glow discharge tube detector, a valve means between said pneumatic source and said channel, and a timer means for periodically onening said valve means to allow said pressure to move said ball in said channel to intercept and block said view path of said glow discharge tube detector.

4. Apparatus as claimed in claim 3 wherein said ball means is a hollow stainless steel ball. 

1. In a fault detection apparatus for a flame scanner system being energized by a glow discharge tube detector, the improvement comprising: ball means, ball actuating means, said ball means being located in relationship to said glow discharge tube detector so as to intercept and block the flame detecting view of said tube detector upon periodic positive actuation thereof by said actuating means, a logic circuit having an AND gate therein, said AND gate receiving independent signals from said glow discharge tube detector and said actuating means indicating positive operating conditions thereof, a fault indicating means operatively connected to said logic circuit so as to be activated when said independent signals reach said AND gate simultaneously.
 2. Apparatus as claimed in claim 1 wherein said ball actuating means comprises a pneumatic pressure means.
 3. Apparatus as claimed in claim 2 wherein said pneumatic pressure means comprises a source of pneumatic pressure, a channel for said ball means, said channel intersecting the path of said flame detecting view of said glow discharge tube detector, a valve means between said pneumatic source and said channel, and a timer means for periodically opening said valve means to allow said pressure to move said ball in said channel to intercept and block said view path of said glow discharge tube detector.
 4. Apparatus as claimed in claim 3 wherein said ball means is a hollow stainless steel ball. 